Latch mechanism for hatchway leaf

ABSTRACT

A safety latch mechanism for a hatchway in which a downwardly extending hook from the free edge of the hatch leaf is engaged by an upper catch end of a lever which is pivoted between its ends by a pin riding in a slot in a horizontal member. The pin is held by a fusible link, while the lower end of the lever is biased by spring actuated means in a direction to maintain the hook and catch end of the lever in releasable engagement. In one embodiment, the spring actuated means is a collapsible toggle linkage and spring. In a second embodiment, the spring means is applied directly to the lower end of the lever. Manual means are provided to actuate the lever to release the latch mechanism. When the fusible link melts, the pin moves outwardly in its slot to move the upper end of the lever to disengage the hook, the lower end of the lever being held relatively stationary. The mechanism is adaptable to latch just one leaf of a hatchway, or may be made with two catches and associated members for two hatch leaves, with the fusible link connecting the pins of each lever so that when the fusible link melts, the pin of each lever can move in its respective slot to release both catches.

Levine States Patent [191 LATCH MECHANISM FOR HATCHWAY [73] Assignee: Babcock-Davis Associates Inc,

Boston, Mass.

22 Filed: Sept. 13,1973

21 Appl. No.: 396,896.

Related US. Application Data [63] Continuation-impart of Ser. No. 238,453, March 27,

1972, abandoned.

[52] US. Cl. 49/8, 98/86 [51] Int. Cl EOSf 15/20 [58] Field of Search; 49/1, 3, 4, 5, 7, 8; 292/225, 246, 247, 50; 98/42, 86

[56] References Cited UNITED STATES PATENTS 3,182,581 5/1965 Von Poederoyen ct a1. 49/8 X 3,332,438 6/1967 Korff 49/8 X 3,337,991 8/1967 Adams 49/3 3,399,500 9/1968 Shapiro 1 49/8 X 3,516,197 6/1970 Lyons 49/1 FOREIGN PATENTS OR APPLICATIONS 469,276 5/1914 France 292/225 1451 Aug. 20, 1974 Primary Examinerl(enneth Downey Attorney, Agent, or Firm-Kenway & Jenney ABSTRACT hatch leaf is engaged by an upper catch end of a lever which is pivoted between its ends by a pin riding in a slot in a horizontal member. The pin is held by a fusible link, while the lower end of the lever is biased by spring actuated means in a direction to maintain the hook and catch end of the lever in releasable engagement. In one embodiment, the spring actuated means is a collapsible toggle linkage and spring. In a second embodiment, the spring means is applied directly to the lower end of the lever. Manual means are provided to actuate the lever to release the latch mechanism. When the fusible link melts, the pin moves outwardly in its slot to move the upper end of the lever to disengage the hook, the lower end of the lever being held relatively stationary. The mechanism is adaptable to latch just one leaf of a hatchway, or may be made with two catches and associated members for two hatch leaves, with the fusible link connecting the pins of each lever so that when the fusible link melts, the pin of each lever can move in its respective slot to release both catches,

17 Claims, 9 Drawing Figures I LATCH MECHANISM FOR HATCHWAY LEAF This application is a continuation-in-part of U.S. Patent application, Ser. No. 238,453, filed Mar. 27, 1972 now abandoned.

BACKGROUND OF THE INVENTION It is recognized that there is a need for means for automatically venting heat and smoke in the event of a tire occurring in the building. It is desired that such vents or hatchways (which are generally located in the roof of the building) automatically be opened when intense heat of a fire occurs, and this is done by the use of fusible links. On the other hand, it is often desirable that such hatchways be manually or electromagnetically openable either from inside or outside the building. In order that the leaf or leaves of the hatchway will open automatically, they are spring biased into the open position. In order to satisfy the Factory Mutual Engineering Association standards for such hatchways and their release mechanisms, it has been established that the vent lids or leaves shall be capable of opening against a lb. per square foot of simulated snow or wind load on the top surface thereof, and lock in the wide-open position. Such vent lids or leaves are not to open when subjected to a 30 lb. per square foot up-lift pressure, such as might be caused by the expansion of heated air inside the building or by the flow of air across the top of the hatchway. In addition, such leaves must be so built that in their vertical open position they will withstand the force of a horizontal wind-load equivalent to 10 lbs. per square foot.

It is readily understood that in view of the above requirements and the fact that the automatic spring loaded hinge mechanisms that actuate the leaves to the open position are quite strong, the latch mechanism used to hold the leaf or leaves in their closed positions must be also quite strong. On the other hand, this imposes the problem that if too much tensile force is exerted on a fusible link which is holding the latches in the closed position, it may seriously interfere with the calibration of the fusible link particularly in view of frictional forces involved. The requirements of the Underwriters Laboratories and the Factory Mutual Engineering Association is that these linkages be standardized to melt at approximately 160F. without fail, and not undergo nuisance trip-out.

A further requirement of the above type of latch is that the latch be openable manually either from inside the building or outside. An added requirement, if it can be obtained, is that such vents may be operable electromechanically in a simple eff cient and fool-proof manner. As an example of the latter, it may be desired that electrically operated solenoids be used to open the latches, these solenoids themselves being operated by thermosensors located in the various parts of the building which it is desired to protect. Of course, it is necessary that the latch mechanisms operate without failure at all times.

SUMMARY OF THE INVENTION Accordingly, it is the general purpose of this invention to provide a linkage type latch mechanism incorporating a fusible link, which will accomplish all of the above desired features in a simple, efiicient and virtually fool-proof manner.

Among the several provisions and advantages of the invention may therefore be notedthe following.

One object of the invention is the provision of. a latch mechanism for a hatchway, in which the mechanism may be actuated either by a fusible link, or by mechanical means, or by electromechanical means.

Another object of the invention is the provision of a latch mechanism of the above class, which is adaptable for application to either a single leaf vent, or to a double leaf vent.

Still another object of the invention is the provision of latching means of either of the above classes, in which the device is operated by a fusible-link, and in which a fused link may be readily replaced.

A further object of the invention is the provision of latching means of any of the above classes, in which a single latching lever has means permitting two motions, in either of which motions the latch is released.

Another object of the invention is the provision of a latching mechanism in which the parts therefor may be stamped from a sheet of metal without expensive milling operations, etc, thus leading to low cost without detracting from the efficiency and safety of the latching mechanism itself.

A further object of the invention is the provision of a latching means of any one or more of the above classes, which is capable of withstanding the'physical requirements of such devices without jamming.

Yet another object of the invention is the provision of latching means of any one or more of the above classes, in which the fusible link is stressed a minimum amount, thus, leading to better accuracy and calibration thereof.

A further object of the invention is the provision of a latch mechanism several of whose parts can be adapted without change for use in two embodiments of the invention.

Other objects, features and advantages will be in part apparent and in part pointed out hereinafter.

The invention comprises the elements, combinations of elements, arrangements of parts, features of construction, and steps and sequence of steps and features of operation, all of which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the appended claims.

In the accompanying drawings, in which are illustrated two of the various embodiments of the invention:

FIG. 1 is an elevation, partly in section, showing a two-leaf hatchway with the latching mechanism of this invention applied thereto, the figure showing one leaf in full and the other in part, the leaves meeting at the middle of the hatchway;

FIG. 2 shows the inner edges of the hatchway leaves just after they have been released from the latch, the figure showing the latching mechanism having been operated manually;

FIG. 3 is a view similar to FIG. 2, but showing the latching means having been operated by release of the fusible link;

FIG. 4 is an elevation, partly in section, showing a second embodiment of the invention, as applied to a hatchway having just one leaf;

FIG. 5 is an end elevation of the latching means of the previous figures; and

FIGS. 6 and 7 show one method of attaching the several pivot points and catch release to the respective links of the latch mechanism;

FIG. 8 is an elevation of a third embodiment of the invention applied to double hatch leaves; and

FIG. 9 is an elevation of a fourth embodiment adapted for use with a single hatch leaf.

Similar reference characters indicate corresponding parts throughout the several views of the drawings; and in the drawings dimensions of certain of the parts may have been modified and/or exaggerated for the purposes of clarity of illustration and understanding of the invention.

Referring now to FIG. 1, a hatchway leaf 2 (shown broken with a portion omitted for purposes of clarity) is shown, hinged at the left-hand end by a spring biased hinge mechanism illustrated generally by numeral 4, this hinge mechanism being clearly shown and taught by US. Pat. No. 3,209,392 issued Oct. 5, 1965 to Nathan Levine. Briefly, the mechanism comprises the pivoted hinge arm 6, one end of which is pivoted to the frame of the hatchway by the pivot 8 and the other end of which is attached to the hatchway leaf 2 by member 10. The arm 6 is engaged through a link 12 to a compression spring 14. When the free edge of the leaf is released by opening of the latch mechanism, the spring 14 will move the leaf to the upright position shown in dotted lines in FIG. 1.

In FIG. 1 the latching mechanism is shown as applied to the type of hatchway in which two leaves are provided, the free edges of the leaves meeting at the center of the hatchway at a typical gutter 16 to provide water run-off. In this drawing, a portion 18 of the other leaf is shown, the portion shown being sufficient to show the application of the latch mechanism also to this other leaf.

Mounted adjacent each free edge are the hook members 20 and 22, these extending in a generally downward direction, and each having a sloping catch surface 24 and 26 respectively.

Mounted on the base of the hatchway by conventional means such as the angle iron 30 (which spans the hatchway) and the two upright support members 32 (this combination being hereinafter called the base) is a horizontally extending elongated member 34. Conveniently, member 34 may be made of an inverted U- shaped angle iron (see FIG. with the web of the member removed at each end at portions 36 and 38 for reasons which will be explained below. In addition, the central portion of one of the downwardly extending sides of this member is also relieved or opened as indicated at 40 for the purpose described below.

At each end of member 34, there is provided a pair of slots, slot 42 at one end and slot 44 being at the other end. It will be noted that the slots at each end are aligned with each other, and that the slots preferably slope slightly upwardly, although these slots can extend horizontally. The preferred angle is between 7and 8. In actual practice, an angle of 7 has been used and found to work satisfactorily.

Levers or links 48 and 50 extend upwardly between the sides of member 34 as shown, and these levers are pivotally attached to the member 34 by means of pivot pins 52 which slide in the slots 42 and 44 and which are attached to the levers between the ends thereof. Each of the levers comprises the two side by side members 54 and 56 (see FIG. 5), these side members being suitably spaced apart and held by the spacer sleeves S8 which are dimensioned suitably for the intended purpose.

It is to be noted that the hook 20 and 22 will exert pulling force on their respective levers 48 and 50, which force is applied to the pins 52 and resisted by the upper edges of the slots 42 and 44. In respect to this, it also is to be noted that in general the slots 42 and 44 are approximately at a angle to the direction of said force. Said angle should lie within the range of 70 to At the upper end of link or lever 48 is provided a catch which comprises a pin 60 and a rotatable sleeve 62 thereon. The purpose of this construction is to minimize the friction between the catch and the sloping surface 24 of the hook 20. In similar fashion, at the upper end of the lever 50 is provided a catch comprising the pin 64 and the rotatable sleeve 66 thereon.

At the lower end of lever 48 is pivotally attached a link 68 by means of the pin 70 which extends through the lower ends of the side members 54 and 56. Spacers 58 (see FIG. 5) of suitable length are provided on the pin 70 to space the link 68 in the position shown in FIG. 5.

In similar manner, a link 72 is attached by means of a pin 74 to the lower end of the lever 50, suitable spacers being provided (as above) .to position link 72 as shown in FIG. 5.

It will be noted that the positioning of the links 68 and 72 by means of the spacers is such that the links are spaced apart slightly. Their lower ends are connected by the pin 76.

A pin 78 extends through the two dependent sides of the member 34, approximately at the center, and a tension spring 80 has one end attached by means of hook 82 to pin 78 and thus to the member 34. The lower end of spring 80 is attached by means of hook 84 to the pin 76 A rope or cable 86 has one end extending through the hatchway housing 88 with a suitable termination such as ball 90 thereon. The cable extends around a fixed pin 92 attached to the strut 30, and is then bent around the pin 78 and attached to pin 74. A second cable 94 is bent around the pin 92, around the pin 78, and is attached to the pin 72. An electromagnet (although this is not necessary unless it is desired to actuate the latch mechanism by means of a push-button or thermal sensor elsewhere located in the plant) is also fastened to the base 30, and to its plunger 102 is attached one end of a short cable 104. The other end of cable 104 is attached by a suitable wrapping or binding 106 to cable 86. Cable 94 is bound to cable 86 by a suitable wrapping or binding 108. As a result of these attachments, if any one of the cable 86, cable 94, or cable 104 is pulled, the result is to pull the pins 70 and 71 toward the pin 78, thus straightening the toggle members 48, 68 and 50, 72.

One end of each of links 110 and 112 is attached, respectively, to one of the pins 52. The other end of each of these links is replaceably joined by the fusible link 114. Links 110 and 112 are of such length that when the fusible link is in place, the pivots 52 are upheld against the inner ends of the slots 42 and 44. In the FIG. 1 position, the lower ends of levers 48 and 50 are so positioned by links 68 and 72 that the catches 60, 62 and 64, 66 engage the hook surfaces 24 and 26 to hold the vent leaves in closed position.

The operation of the device is as follows. Referring to FIG. 2, and explaining first the manual release of the latch, the ball 96 is pulled which pulls the cable 94.

This in turn pulls cable 86. As a result, both of the pins 70 and 74 are pulled towards the pin 78, the levers 48, 50 are rotated about their pins 52 to move the catches 60, 62 and 64, 66 off their respective hooks. FIG. 2 shows the positions of the leaves 2 and 18 shortly after hooks 2t and 22 have been released by their respective catches, and the springs 14 of the respective leaves have moved these leaves in an upward direction toward their final resting position. It is to be noted that when the leaves are in the closed position, the sloping surfaces 24 and 26 of the hooks 20 and 22 will assist in the releasing action.

When the cables 94 and 86 are released, tension spring 80 will return the pin 76, and the pins 72 and 74 with their respective linkages to the position shown in FIG. 1, thus positioning the catches to'be reengaged by their hooks when the leaves are closed.

Pulling cable 86 directly by means of bell 90 will also open the latches to release the'leaves. Instead of pulling the ball 96 or the ball 90, the electromagnet 100 may be actuated by suitable means with the result that the plunger 102 will pull cable 104 which in turn pulls cable's 86 and 94, and thus pins 70 and 74 are pulled toward the pin 78 effectuating the release of the catches 60, 62 and 64, 66 from their respective hooks 20 and 22.

Referring now to FIG. 3, the operation of the device is described in the event that an excess of heat melts the fusible link 114. Upon the link melting, the pins 52 are released to slide outwardly in their slots, and the releasing forces exerted by the sloping faces 24, 26 of the hooks 20, 22 become effective to cause the latches to roll off the hooks, thus freeing the leaves to swing to an open position. It will be noted that the pins 70 and 74, remain relatively stationary in a predetermined position with respect to the base of the linkage, being held so by the links 68 and 72. In using the wordrelative in respect to the pins 70 and 74, it will be observed that a dual function as to the links 48 and 50 is accomplished in the sense that the tension spring 80 will exert a force on pin 76 in an upward direction. This will tend to relieve any frictional forces in the latches, and as between the pins 52 and their slots.

As illustrated in FIG. 3, the fusible link has melted and separated, with the result that the links 110 and 112 have dropped downwardly to come to rest against the stop pins 116 which are affixed to the uprights 32. (When the latch is actuated manually, the lower end of the levers 48 and 50 will strike the same stop pins.)

To replace the fusible link, which is preferably done while the leaves are open, links 110 and 112 are placed in their initial horizontal positions, and pulled toward each other to pull the pins 52 to the inner ends of their slots. In this position, the melted fusible link 114 may then be removed, and a new one put in place.

This having been done, the leaves may be closed, with the sloping bottom edges 118 acting as cams to move the catches outwardly so they can ride up and over the hook surfaces 24 and 26. In such action, the levers 48 and 50 rotate on pins 52 against the restraining force of spring 80.

Referring now to FIG. 4, there is shown a second embodiment in which the invention is shown applied to a hatchway having a single leaf and having, for example,

the same kind of biased hinge structure shown in FIG. 1. In this instance, a single leaf 120 (like leaf 2, forexample) is attached by the biased hinge structure (not shown) of the FIG. 1 embodiment to casing 122 of the hatchway or vent. Horizontal member 124 (which corresponds to member 34) is provided, butin this instance is attached firmly by one end thereof to the casing 122. Member 124 has its central portion opened, as at 126 to allow access to a fusible link 114 the same as is used in the FIG. 1 embodiment, but has only one slot 125. A pair of connecting links 128 and 130 are used, one end of the link 130 being attached to the fusible link 114 and the other end being attached by means of a pin 132 to the member 124. Link 128 has one end attached to the other end of fusible link 114, and the other end of link 128 is attached to pin 52 which slides in slot 125 corresponding to slot 42 of the FIG. 1 embodiment.

The web of member 124 is relieved at its end in order to permit the entry, between the remaining sides, of lever 48 which is held by means of the pin 52 in slot 125. The upper end of the lever 48 is provided with the pin 60 and the catch sleeve 62 which engages'the sloping surface 24 of a hook 20, the latter being attached to the under surface of leaf 120; all as in the FIG. 1 embodiment.

In a manner similar to the FIG. 1 embodiment, there is attached to the lower end of lever 48 by means of pin 70 the link 68 whose lower end is attached to pin 76 to a link 72. The latter is attached by means of a pin 134 to a support member 136 which is attached to the casing 122. If desired, member 136 may be an integral part of member 124.

In this embodiment, mechanical means for actuating the device (in addition to the fusible link) are shown. A ball 138 which is attached to a cable 140, the latter being trained around an extension of a pin 78 which, as in the previous embodiment, is attached to the member 124. The other end of the cable 140 is attached to the pin 70. In addition, an external release mechanism is provided; namely the ball 142, which is attached to the cable 144 which extends through a suitable hole in the hatch housing, is trained over the pin 78, and is attached to the link 70 at the attachment point 146.

As in the previous embodiment, a tension spring 80 has one end attached to the pin 76 and the other end attached to pin 78.

The operation of this embodiment is about the same as that of FIG. 1 embodiment. A pull on either of the balls 138 or 142 will move the pin 70 toward the pin 78, with the result that the lever 48 rotates about the pivot pin 52. The upper end of the link 48 swings to the left (as viewed), so that it slides off the sloping surface 24 of the hook 20 to release the latch and let the vent leaf spring open.

On the other hand, if the fusible link 114 is melted by over-heating, then it separates to release the link 128, so that the pin 52, under the combined bias of the sloping surface 24 exerted through the catch 60, 62, will move to the left in its slot 125, thus moving the upper end of lever 48 to free the catch from hook 20. Replacement of the fusible link follows the procedure described for the FIG. 1 embodiment.

With this construction, it will be noted that the force exerted in an upward direction by the leaf (due to the spring hinging and to expanded gasses in the building) is transmitted to the hooks 20 and 22. However, only a minor portion of this force is ever applied to the fusible link; the reason being that the force is exerted fully on the pins 52 and is therefore resisted by the upper edges of the slots 52, ie., by the support member 34. Only a very minor component of this force, if any at all, is directed to be in line with the length of the fusible link. As a result, the calibration of the device is made more constant.

While the details of the type of pivot pins used are not critical, nevertheless, FIGS. 6 and 7 are presented herein to show convenient and workable pins. In an exemplary fashion, the upper end of the two members 54 and 56 making the lever 48 are shown. The pin 60 is shown with head 148 and a body which extends through both of the members 54 and 56. The pin is anchored at the other end by means ofa C ring 150 which tits in a peripheral groove in the pin. The sleeve 62 is shown mounted on the pin 60. Suitable washers 152, one at each end, are provided as is customary.

Referring now to FIG. 8, a third embodiment is shown incorporating a different means for biasing the latch levers 160 and 162 into latching position. As before a central support 164 is provided like that of FIG. 1, made of angle-iron and having slots 166, 168 at the ends, the slots being angled upwardly, as shown, approximately 7 to 8 from the horizontal. Support 164 is mounted on plate 165 which fastens to the framework of the hatchway, such as to a cross beam 167. Pins 170, 172 ride in the slots as in the FIG. I embodiment, and pass through the ends of, respectively, links 174 and 176. The other ends of the links are connected by a fusible link 178, links 174, 176 being of such length that when connected by the fusible link, pins 170, 172 are held against the inner ends of their respective slots.

The upper ends of levers 160, 162 are provided with pins 180, like pins 60 of FIG. 1, which engage the catch faces of hooks 182, 184 which are attached to the hatch leaves 2, 18. It will be noted that in this embodiment, the catch faces 186 of the hooks are approximately at right angles to the lengths of the hooks. To establish the angular relation of the faces 186 to the horizontal described above in respect to the FIG. 1 embodiment, the bodies of the hooks are inclined at a greater angle to the vertical than in the former embodiments. Thus, there will be effectuated a component of force on each pin 170, 172 caused by the upwardly spring-biased leaves and acting through the angled catch faces 186 which tends to move the pins off the respective catch faces to release the hatch leaves. This component of force exerts a first moment about each of the pins 170, 172 which is resisted by biasing means indicated generally by numeral 188 (described below) which exerts a second moment opposite the first moment sufficient to keep the hooks and pins engaged. However, as in the FIG. I embodiment, when the link 178 melts, the pins 170, 172 are caused by the first moment of force respectively, to move outwardly in their slots to release the pins 186 from their respective hooks.

Each of biasing means 188 comprises a bracket 190 mounted on the support 165 in fixed relation to the support 164 as shown. A slide bar 192 slides through a hole in each bracket, and has an eye 194 at one end which fits over a pin 196 which engages the respective lever 160 or I62 below pins 170, 172 but above the lower ends of the levers. A washer is provided on each slide bar to act as an abutment for one end of a compression spring 198, the other end of which bears against its respective bracket. Springs 198 are each strong enough to resist the moment forces exerted by the sloping faces of the hooks on their levers about the pins 170, 172.

Attached to the lower ends of the levers 160, 162 by means of conventional pin engagements are cables 200. Each cable is trained over its respective pulley 202 and is joined to a single cable 204. The latter is in turn trained over pulley 206 on beam 167 and extends to the place where, as desired, a handle may be attached (not shown) for pulling the cable. When cable 204 is pulled to open manually the hatch leaves, it pulls the lower ends of the latch levers toward each other, compressing the springs 198 and rotating the levers about pins 170, 172 as fulcrums. This moves pins 180 off their respective hook faces to-release the hatch leaves.

Referring now to FIG. 9, a fourth embodiment of the invention is shown which adapts a portion of the FIG. 8 embodiment to a single hatch leaf 120. An angle-iron support 210 is attached approximately horizontally to a support member 212 which in turn is attached to a convenient beam or other portion 214 of the hatchway framework below the hatch leaf 120. A second support 216 assists in mounting the angle-iron support. The latter has a slot 218 at one end thereof in which slides a pin 170 as in the FIG. 8 embodiment. A link 220 is attached to pin 170, and is engaged at its other end by the fusible link 178. The other end of the latter is fastened to the support 210.

Lever 160, pin 180, hook 182, hook face 186, bracket 190, slide bar 192, pin 196, and compression spring 198 are the same as in the FIG. 8 embodiment, and relate to each other and to the horizontal and vertical in the same way. A cable 222 is fastened to the lower end of lever 160, is trained over pulleys 224 and 226 and then extends to the position desired where a handle may be attached for pulling on the cable.

The operation of this embodiment is the same as that of FIG. 8. Pulling cable 222 will swing lever about pin to release the leaf 120. Melting of the fuse link 178 will allow pin 170 to move to the left (in its slot) under the compulsion of the moment of force acting on the upper end of lever 160 due to the angular relation of the face 186 to the horizontal, thus providing automatic opening of the hatch leaf.

In the FIGS. 8 and 9 embodiments, stop members 228 are provided to position the levers (after the hatch leaves have opened) so that on closing the leaves, the proper engagement of the respective hooks and pins can take place. Without such stops, the levers would be rotated by the springs 198 about pins 170 and 172 so far as to cause pins to lie too far away from the hooks to be engaged thereby.

In view of the above it will be seen that the several objects of the invention are achieved and other advantageous results attained.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseol-' As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all such equivalent variations as come within the true spirit and scope of the invention.

What is claimed is:

l. A latch mechanism for a hatchway leaf which is hinged at one edge to the hatchway for opening and closing the latter, the hatchway including means applying a force to the leaf to bias it toward the open position, said mechanism comprising:

a hook extending from the leaf adjacent the free edge thereof; a an elongated support member fixed to the hatchway;

a lever extending toward the hook;

catch means at one end of the lever adapted to engage the hook;

a pivot pin engaging the lever between the ends thereof, the pivot pin being attached to the support member and linearly movable with respect thereto in a first direction from a first position to a second position to release the catch means from the hook, and being restrained against motion in a second direction, the pivot pin while in the first position constituting a pivot about which the lever is adapted to rotate to release the catch means from the hook;

a fusible link, one end of which is attached to the pivot pin and holds the latter in said first position while the fusible link is in solid state, the other end of the fusible link being restrained against motion in said first direction;

mechanically actuable means attached to the other end of the lever for rotating the latter about the pivot pin when the latter is in its first position, thereby to release the catch means from the hook; and

first biasing means urging the pivot pin in said first direction when the leaf is in closed position, whereby when the fusible link melts, the pivot pin is freed and moves, under the influence of said first means, in said first direction to permit said one end to move in a direction to release the catch means from said hook.

2. The latch mechanism of claim 1 including second biasing means resiliently biasing the lever in latch closing direction.

3. The latch mechanism of claim 2 in which said first biasing means is a sloping surface on the hook engaging said catch means.

4. The latch mechanism of claim 2 in which a slot is provided in the support member, the pivot pin being slidable in the slot in said first direction, and the lengthwise direction of the slot coinciding with said first direction, the latter being at an angle to the direction of the force exerted by said lever on the pivot pin, said angle being in the range of 70 to 80.

5. The latch mechanism of claim 4 in which the force exerted by said lever on the pivot pin is approximately perpendicular to the lengthwise direction of the fusible link.

6. The latch mechanism of claim 4 in which said fusible link, while in a solid state, holds the pivot pin against one end of said slot.

7. The latch mechanism of claim 2 in which the second biasing means includes a first link having one end pivotally attached to the other end of the lever, a second link having one end pivotally attached to the other end of the second link, means pivotally holding the other end of the second link immovable at least while the fusible link is in a solid state, and a spring connected between the joint between the two links and the support member and applying a resilient force tending to move said joint in a direction to swing said lever into a latch closing position.

8. A latch mechanism for a hatchway leaf having two leaves hinged at their outer edges and their inner edges meeting at the center of the hatchway when the latter is closed, each leaf being resiliently biased toward open position, comprising:

a pair of books extending inwardly of the hatchway,

one from each adjacent leaf edge portion;

an elongated support member fixed to the hatchway below said hooks when the leaves are closed;

first and second levers, one for each hook and extending theretoward;

catch means at the upper end of each lever adapted to engage its respective hook;

a pivot pin attached to each lever between the ends thereof, each pivot pin being attached to the support member and linearly movable with respect thereto in a respective first direction from a first position to a second position to release the catch means from the respective hook, the pivot pins being movable with respect to each other and the respective first directions being away from each other, each pivot pin being restrained against motion in a second direction and each pivot pin while in the first position constituting a pivot about which its respective lever is adapted to rotate to release the respective catch means from its hook;

a fusible link whose ends are attached to the pivot pins to hold the latter in a fixed inwardly disposed relation to each other and in relation to the support member while the fusible link is in solid state;

mechanically actuable means attached to the other ends of the levers for rotating the latter about their respective pivot pins when the latter are in their first positions, into latch opening position, thereby to release the catch means from the hooks; and

first biasing means urging the pivot pins in opposite directions when the leaves are in closed position whereby, when the fusible link melts, each pivot pin is freed and moves, under the influence of said first means, in its respective first direction to permit the catch end of its respective lever to release the catch means from the respective hook.

9. The latch mechanism of claim 8 including second biasing means resiliently biasing each lever in latch closing direction.

10. The latch mechanism of claim 9 in which said first biasing means is a sloping surface on each of the hooks engaging the respective catch means of each lever.

11. The latch mechanism of claim 9 in which a pair of slots are provided in the support member, each pivot pin being slidable in one of the slots in its respective first direction, and the lengthwise direction of the slot coinciding with said respective first direction, each first direction being at an angle to the direction of the force exerted by each of said levers on the respective pivot pin, said angle being in the range of 80 to 90.

12. The latch mechanism of claim 11, in which the force exerted by each of said levers on its respective pivot pin is approximately perpendicular to the length wise direction of the fusible link.

13. The latch mechanism of claim 11 in which said fusible link, while in a solid state, holds the pivot pins against one end of the respective slot.

14. The latch mechanism of claim 9 in which the second biasing means includes a first link having one end pivotally attached to the other end of one of said levers, a second link havine one end pivotally attached to the other end of the other of said levers, the other ends of said links being pivotally held together, and a spring connected between the joint between the two links and the support member and applying a resilient force tendl2 ing to move said joint in a direction to swing both of said levers into a'latch closing position. 15. The latch mechanism of claim 2 in which the second biasing means comprises a spring having one end mounted in fixed relationship to the support member,

and having its other end attached to said lever at a posi-' tion thereon such that the biasing force of the spring acts in a direction to resiliently restrain the lever in latch closing position.

16. The latch mechanism of claim 2 in which the second biasing means comprises a spring having one end attached to the support member and the other end attached to that end portion of the lever which lies, with respect to the pivot means, remote from the catch means.

17. The latch mechanism of claim 16 in which said spring is a compression spring. 

1. A latch mechanism for a hatchway leaf which is hinged at one edge to the hatchway for opening and closing the latter, the hatchway including means applying a force to the leaf to bias it toward the open position, said mechanism comprising: a hook extending from the leaf adjacent the free edge thereof; an elongated support member fixed to the hatchway; a lever extending toward the hook; catch means at one end of the lever adapted to engage the hook; a pivot pin engaging the lever between the ends thereof, the pivot pin being attached to the support member and linearly movable with respect thereto in a first direction from a first position to a second position to release the catch means from the hook, and being restrained against motion in a second direction, the pivot pin while in the first position constituting a pivot about which the lever is adapted to rotate to release the catch means from the hook; a fusible link, one end of which is attached to the pivot pin and holds the latter in said first position while the fusible link is in solid state, the other end of the fusible link being restrained against motion in said first direction; mechanically actuable means attached to the other end of the lever for rotating the latter about the pivot pin when the latter is in its first position, thereby to release the catch means from the hook; and first biasing means urging the pivot pin in said first direction when the leaf is in closed position, whereby when the fusible link melts, the pivot pin is freed and moves, under the influence of said first means, in said first direction to permit said one end to move in a direction to release the catch means from said hook.
 2. The latch mechanism of claim 1 including second biasing means resiliently biasing the lever in latch closing direction.
 3. The latch mechanism of claim 2 in which said first biasing means is a sloping surface on the hook engaging said catch means.
 4. The latch mechanism of claim 2 in which a slot is provided in the support member, the pivot pin being slidable in the slot in said first direction, and the lengthwise direction of the slot coinciding with said first direction, the latter being at an angle to the direction of the force exerted by said lever on the pivot pin, said angle being in the range of 70* to 80*.
 5. The latch mechanism of claim 4 in which the force exerted by said lever on the pivot pin is approximately perpendicular to the lengthwise direction of the fusibLe link.
 6. The latch mechanism of claim 4 in which said fusible link, while in a solid state, holds the pivot pin against one end of said slot.
 7. The latch mechanism of claim 2 in which the second biasing means includes a first link having one end pivotally attached to the other end of the lever, a second link having one end pivotally attached to the other end of the second link, means pivotally holding the other end of the second link immovable at least while the fusible link is in a solid state, and a spring connected between the joint between the two links and the support member and applying a resilient force tending to move said joint in a direction to swing said lever into a latch closing position.
 8. A latch mechanism for a hatchway leaf having two leaves hinged at their outer edges and their inner edges meeting at the center of the hatchway when the latter is closed, each leaf being resiliently biased toward open position, comprising: a pair of hooks extending inwardly of the hatchway, one from each adjacent leaf edge portion; an elongated support member fixed to the hatchway below said hooks when the leaves are closed; first and second levers, one for each hook and extending theretoward; catch means at the upper end of each lever adapted to engage its respective hook; a pivot pin attached to each lever between the ends thereof, each pivot pin being attached to the support member and linearly movable with respect thereto in a respective first direction from a first position to a second position to release the catch means from the respective hook, the pivot pins being movable with respect to each other and the respective first directions being away from each other, each pivot pin being restrained against motion in a second direction and each pivot pin while in the first position constituting a pivot about which its respective lever is adapted to rotate to release the respective catch means from its hook; a fusible link whose ends are attached to the pivot pins to hold the latter in a fixed inwardly disposed relation to each other and in relation to the support member while the fusible link is in solid state; mechanically actuable means attached to the other ends of the levers for rotating the latter about their respective pivot pins when the latter are in their first positions, into latch opening position, thereby to release the catch means from the hooks; and first biasing means urging the pivot pins in opposite directions when the leaves are in closed position whereby, when the fusible link melts, each pivot pin is freed and moves, under the influence of said first means, in its respective first direction to permit the catch end of its respective lever to release the catch means from the respective hook.
 9. The latch mechanism of claim 8 including second biasing means resiliently biasing each lever in latch closing direction.
 10. The latch mechanism of claim 9 in which said first biasing means is a sloping surface on each of the hooks engaging the respective catch means of each lever.
 11. The latch mechanism of claim 9 in which a pair of slots are provided in the support member, each pivot pin being slidable in one of the slots in its respective first direction, and the lengthwise direction of the slot coinciding with said respective first direction, each first direction being at an angle to the direction of the force exerted by each of said levers on the respective pivot pin, said angle being in the range of 80* to 90*.
 12. The latch mechanism of claim 11, in which the force exerted by each of said levers on its respective pivot pin is approximately perpendicular to the lengthwise direction of the fusible link.
 13. The latch mechanism of claim 11 in which said fusible link, while in a solid state, holds the pivot pins against one end of the respective slot.
 14. The latch mechanism of claim 9 in which the second biasing means includes a first link having one end pivotally attached to the oTher end of one of said levers, a second link havine one end pivotally attached to the other end of the other of said levers, the other ends of said links being pivotally held together, and a spring connected between the joint between the two links and the support member and applying a resilient force tending to move said joint in a direction to swing both of said levers into a latch closing position.
 15. The latch mechanism of claim 2 in which the second biasing means comprises a spring having one end mounted in fixed relationship to the support member, and having its other end attached to said lever at a position thereon such that the biasing force of the spring acts in a direction to resiliently restrain the lever in latch closing position.
 16. The latch mechanism of claim 2 in which the second biasing means comprises a spring having one end attached to the support member and the other end attached to that end portion of the lever which lies, with respect to the pivot means, remote from the catch means.
 17. The latch mechanism of claim 16 in which said spring is a compression spring. 